We have demonstrated the continuous-wave operation of a highly efficient 2.8 μm Er-doped LuO ceramic laser at room temperature. An Er:LuO ceramic with a doping concentration of 11 at.% afforded a slope efficiency of 29% and an output power of 2.3 W with pumping at 10 W. To our knowledge, these are the highest slope efficiency and output power obtained to date for an Er:LuO ceramic laser at 2.8 μm. In addition, we prepared ceramics with various doping concentrations and determined their emission cross sections by fluorescence lifetime measurements and emission spectroscopy.

This paper describes the effects of nonstructural brick walls on the seismic performance of reinforced concrete (R/C) buildings. Experimental and analytical studies were conducted on two buildings: one of which collapsed and the other suffered moderate damage due to the 2007 Sumatra, Indonesia earthquakes. A brick wall was extracted from the moderately damaged building and transported to Japan from Indonesia to experimentally evaluate its seismic performance. Two R/C one-bay frame specimens were constructed, and the imported wall was installed in one of the specimens. Comparing the seismic performance of specimens with and without the brick wall through quasi-static cyclic loading tests, wall contributions were quantitatively evaluated. Moreover, the seismic performance of the earthquake-damaged Indonesian buildings was evaluated numerically considering the findings of the tests. The analyses revealed a possible reason for the collapse of one of the buildings due to the earthquakes.

We have demonstrated a passively Q-switched Er:Lu2O3 ceramics laser using a monolayer graphene saturable absorber. Stable pulsed operation with watt-level average power was achieved by a compact linear cavity without focusing on the saturable absorber. This is the first demonstration of a passively Q-switched mid-IR Er:Lu2O3 laser using a graphene saturable absorber. A maximum pulse energy of 9.4 μJ and a peak power of 33 W were achieved with a 247 ns pulse duration. To our knowledge, this is the shortest pulse duration, highest pulse energy, and highest peak power obtained with a graphene saturable absorber in the 3 μm wavelength region.

We present a high-power, high-efficiency, laser-diode-pumped 2.8 μm Er:Lu2O3 ceramic laser generating record power at room temperature. Careful thermal management and pump-radius enlargement resulted in a continuous-wave output power of 6.7 W at 2845 nm, with a 30.2% slope efficiency. To our knowledge, this is the highest output power and slope efficiency ever achieved from a laser-diode-pumped 3 μm Er-doped ceramic laser. These results confirm the possibility of generating high-output-power, high-efficiency laser using transparent ceramics.

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